Pearlescent pigment

ABSTRACT

The luster, compressibility and other cosmetically important properties of various pearlescent pigments are substantially improved by coating the surface of the pigment particles with a composition comprising a precipitated water-insoluble metal stearate and a surfactant.

llnited States Patent Chapman et al.

1151 3,0503% [45] Apr. 18, 11972 [54] PEARLESCENT PIGMENT Inventors: Douglas W. Chapman, Normandy; Wilbur H. McKellin, Creve Coeur; R. Dean Overley, St. Louis, all of Mo.

Assignee: Mallinckrodt Chemical Works, St. Louis,

Filed: May 4, 1970 Appl. No.: 34,585

us. Cl. 106/291, 106/308 Q, 106/308 F, 106/308 N, 106/308 5 Int. Cl. ..'C09C 3 02 Field 61 Search ..l06/29 1, 308 s, 308 Q, 308'F, 106/308 N Primaly Examiner-James E. Poer Att0rneyJohn D. Pope, Ill

[5 7] ABSTRACT The luster, compressibility and other cosmetically important properties of various pearlescent pigments are substantially improved by coating the surface of the pigment particles with a composition comprising a precipitated water-insoluble metal stearate and a surfactant.

8 Claims, No Drawings PEARLESCENT PIGMENT sion an aqueous solution containing cations which form a water-insoluble soap. Optionally, a water-insoluble surfactant BACKGROUND may be added to the reaction mixture during or following the The present invention relates to the field of pearlescent pig- Preclpltanon ofthe metal Soap ments and more particularly to improved pearlescent pig- DESCRIPTION OF THE PREFERRED EMBODIMENTS .ments for use In various cosmetic formulations.

Certain synthetic pigments are widely used to impart a The present invention is particularly useful and beneficial in pearl-like luster to various substances. Among thos most conjunction with pearlescent pigments which are to be incorwidely used in cosmetic formulations are bismuth oxychloride 1 POraIed Compressed cosmetic powders. Of these the most and mica platelets coated with either bismuth oxychloride or 0 commonly Used are blsmuth OXYChIOHde ry l a mica titanium dioxide. While generally satisfactory, these materials PlateletS Coated with bisthuth oxychloride h titanium dlolfldeare often excessively bulky and deficient in certain properties The pearlescent base P gm t m y ad ionally contam a which are desirable for cosmetic applications, notably slip, Colored P g as described copehdlhg applications of cling" and compressibility. These properties are closely revDouglas Chapman and Deah ovel'ley, 561510376992, lated to the lubricity of the pigment particles. Various metal filed Nov. 14, 1969, and of Douglas W. Chapman, R. Dean soaps such as calcium and magnesium stearates are widely Overley, Robert D. Rands, Jr. and Ronald S. Schreiber, Ser. used as dry lubricants as for example in the manufacture of No. 15,887,filed Mar. 2, 1970 both now abandoned.

tablets where the powdered soap is mixed or blended with the In a simple embodiment of the invention the surface of the other components of the tablet. When, however, these soaps pearlescent pigment particles is first coated with an intimate are used in a similar manner with the above-described pearadherent film or deposit of an insoluble metal soap, such as for lescent pigments the expected improvement in the slip and example calcium stearate or magnesium stearate. This is accompressibility is not realized, and in addition the pearlescent complished by forming and precipitating the metal soap in an luster of the pigment is considerably dulled. aqueous suspension of the pearlescent pigment. The coating It is also known to provide various pigments with a film or 5 obtained in this manner is much more adherent than if the coating of a fatty acid or metal soap dissolved or dispersed in preformed metal soap is merely admixed with the pigment. An some suitable liquid media. in that case the resulting products intimate adherent coating results which substantially improves are in the form of a more or less sticky paste or suspension the om re ibility and lubricity of the pigment arti le rather than in the form of dry free-ilowing particles which are thereby increasing their compatibility and effectiveness in the more useful and desirable. many cosmetic formulations, especially compressed powders.

The term soap is used herein to mean a salt of a higher In addition the precipitated'metal soap coating does not subsubstantially saturated fatty acid or mixture of acids such as stantially dull the luster of the pigment but in some instances palmitic, stearic, myristic, etc.; Le. a saturated aliphatic acid, appears to enhance the luster. Merely admixing a preformed essentially straight-chained and containing 1220 carbon metal soap with the pigment dulls the pigment luster if it does atoms. not obscure it.

Among the objects of the present invention may therefore whe a dry earle nt igme t i oated with a water-inbe noted the provision of novel pearlescent pigments in the soluble metal soap alone, it becomes hydrophobic or waterform of substantially dry free-flowing particles characterized repellent, and this may be a serious disadvantage for certain by their improved slip and cling and by their improved coma li ation a i the a e of certain om res ed powders pressibility. A further object is the provision of methods for 40 which are applied with the aid of a moistened brush. it has treating certain pearlescent pigments in order to substantially b n f nd that the in or oration of a suitable surfactant in increase their usefulness for cosmetic applications, especially the oating not only makes the igments wettable but certain in compressed powders. Other objects and features will be in surfactants act synergistically with the stearate to effect a part apparent and in partpoint d ut hereinafter. further substantial and surprising improvement in the com- The invention accordingly comprises the products and ibilit fth i m t, methods hereinafter described, the scope o th in nti Water-insoluble nonionic surfactants have been found to be being indicated in the following claims. generally more effective and are therefore preferred. It is also desirable that the surfactant have an HLB value (hydrophylic- SUMMARY OF THE INVENTION lipophylic-balance) in the middle portion of the range. A low The present invention is directed toan improved pear- 5O HLB Value i y p y p p y indicates that lescent pigment in the form of substantially dry free-flowing the surfactant is Predominantly P P Y Whereas a high particles consisting essentially of pearlescent base, the parti- Value indicates that it Predominantly p y shtfac cles of which are substantially covered with a precipitated c i tY b l f8 the f abtgut h about 16 coating comprising an insoluble metal soap. Moreover, a surin] pre erathy a out alve beelnbpun rfto t e t e fioithusefactant may advantageously be incorporated in the said metal u thong e Commercla y aval a e ac an S W 1c ave soap i been found useful for the purposes of the present invention The invention is also directed to a method for treating peary be noted! Chemical composition Trade name Manufacturer Type HIJB 100% sorbitan monolaurate 100% polyoxyethyolene (2) cetyl ether.... 100% polyoxyethyelene (10) stearyl ether. 100% sorbitan monostearate 100% polyoxyethylcne sorbitan monolaurate (polysorbato 20). 100% polyethylene (4) sorbitan monostcaratc 100% polyoxyothylnnn sorhitan monooloatox 100% diisnllutylcrusoyl-uthoxyuthyl tlimothyl hrnzyl ammonium chloride...

Tween 81 .ido. lIynmino10 X.... Rolnu & lions. i

100% nunylnhonoxypolyothoxyotlnnml 'Iriton N-67.

30% sodium null. oi ulkylmyl polyutlnr sullonnto 'lrilon X 202. .do

100% mlyoxyutliylunu (K) stonrnte Atlns. Nouionio.v 11.1 10004. polyoxytihylonu ('10) stom'utu lli).. do... 10.0 100'!" dioutyl sodium sullosuocimito. American (ymuimid. Anionic... 1110",. sodium linom' nlkyluto sull'nnnto Atlantic Riolil'wld ..do 1011",.phosphate acid Rolnudzllnns ..do 1000,.othoxylntcd lanolin. Mnlmsttom Nonionic lescent pigments which comprises suspending the pearlescent The surfactant may be incorporated in the metal soap coatptgment in water; dispersing a water-soluble salt of a fatty acid mg in any convenient manner, as for example by adding an in the said suspension and gradually adding to the said suspenaqueous di i f th fa t t t th q u igme t suspension after the precipitation of the metal soap. Altematively, the surfactant may be added simultaneously with the metal salt used to precipitate the soap.

A coating comprising about 1% calcium stearate and 1% of the surfactant based on the weight of the pigment is usually sufficient. Heavier coatings may be applied but these seem to provide little additional benefit. If the coating is too thick it may dull rather than increase the luster ofthe pearlescent base or it may have other undesirable effects. Generally speaking, the optimum coating thickness falls within the range from about 0.5 to about ofthe weight of the pigment.

The following examples illustrate the invention.

EXAMPLE 1 The following illustrates a simple embodiment of the invention wherein a pearlescent pigment is coated with an alkaline earth metal stearate to improve its compressibility. A mixture containing 5 g. of ammonium stearate in 2 liters of water was heated to disperse the stearate, and to it was added 500 g. ofa pearlescent base consisting of mica platelets coated with bismuth oxychloride, (bismuth oxychloride constituting 40% of the total weight of the pigment). An alkali metal stearate such as sodium or potassium stearate may be used in place of ammonium stearate. Pearlescent pigments of this kind are more fully described in the copending application of Robert D. Rands, Jr. and Douglas W. Chapman, Ser. No. 766,614, filed Oct. 10, 1968, now US. Pat. No. 3,597,250. The resulting slurry was cooled to room temperature and diluted with water to 3 liters. A solution containing 1.73 g. MgCl .6H O in 150 ml. of water was added with stirring to precipitate magnesium stearate. The product was collected on a filter, washed with water and dried at 80 C. overnight. It contained 1% magnesium stearate in the form of an intimate adherent coating.

EXAMPLE 2 In the following example a water-insoluble surfactant is incorporated in a calcium stearate coating.

Calcium stearate was precipitated on a pearlescent mica- BiOCl slurry as described in Example 1, and to the resulting slurry was added over a period of about minutes a hot dispersion of 5 g. of Tween 61 in 250 ml. of distilled water. The product was collected on a filter, washed, dried overnight at 80 C., and then passed through a 60 mesh sieve. lt contained approximately 1% calcium stearate and 1% of the surfactant.

Other surfactants such as BRIJ 58, Tween 20 and Tween 81 may be substituted for the Tween 61 and incorporated in a similar manner.

EXAMPLE 3 The invention is also applicable to pearlescent pigments colored with an appropriate metal oxide or other insoluble colored substance of the kind disclosed in copending applications, Ser. No. 876,992 and Ser. No. 15,887 mentioned above. To 650 ml. of distilled water was added 5 g. of sodium stearate and the mixture was heated until the stearate dissolved. This was poured slowly into a stirred suspension of 500 g. of a yellow pearlescent base which consisted of mica coated with bismuth oxychloride and having deposited thereon a yellow iron oxide as described more fully in copending application, Ser. No. 876,992, Example 4. Stirring was continued and a solution containing 1.25 g. CaCl .2H O in 250 ml. of distilled water was gradually added over a period of about minutes. The dried product contained 1% calcium stearate in the form of an intimate adherent coating.

EXAMPLE 4 The invention is also applicable to titanated mica, i.e. mica platelets coated with titanium dioxide, as in the following:

A mixture of l g. ammonium stearate in 130 ml. distilled water was heated to disperse the stearate and then slowly added to a stirred suspension of 100 g. titanated mica (Pearl Afflair" manufactured by duPont) in 300 ml. distilled water. Stirring was continued and a solution of0.25 g. of CaCl .2H O in 50 ml. water was added dropwise during one-half hour. The product was collected and dried as before. It contained approximately l% calcium stearate in the form of an intimate adherent coating.

EXAMPLE 5 Metal salts other than calcium and magnesium may be used to precipitate an insoluble stearate coating, with or without the inclusion of a wetting agent, as follows: To a stirred slurry of 100 g. of 40% BiOCl by weight on mica in 300 m1. of distilled water was added a hot dispersion of l g. of ammonium stearate in 100 ml. of distilled water. Stirring was continued and during 15 min. a solution of0.62 g. AI(NO;,) .9H O in 50 ml. of distilled water was added dropwise. Stirring was continued for 15 minutes then the mixture split into two equal parts, A and B. A was collected, washed with 2 X 50 ml. of distilled water and dried in the steam oven. B was stirred and a hot dispersion of 0.5 g. of Tween 61 poured in. Stirring was continued for 15 minutes, the product collected and treated like A. After drying both were put through a mesh sieve. A and B contained 1% aluminum distearate and B contained in addition 1% Tween 61.

Alternatively the pearlescent base may be coated with other stearates such as nickel stearate, zinc stearate and ferric stearate in a similar manner.

EXAMPLE 6 Nacreous bismuth oxychloride crystals were coated with 0.5% calcium stearate with and without 1% Tween 61 in a manner similar to that described in Example 1. To a stirred suspension of 200 g. of nacreous BiOCl crystals in 500 ml. of distilled water was added slowly a hot dispersion of l g. of ammonium stearate in 200 ml. of distilled water. The mixture was stirred 15 minutes, then a solution of().25 g. CaCl .2H O in 50 ml. of water was added dropwise during 15 minutes. One-half of this mixture (A) was set aside. To the other half (B) was added a hot dispersion of 1 g. of Tween 61 in ml. of distilled water. Both A and B were collected, washed with 2 x 50 ml. of water, dried in the steam oven and passed through a 60 mesh sieve.

Both A (hydrophobic) and B(wettable) showed improved slip and compressibility compared with the original crystals, but B which also contained Tween 61 was significantly better than A which contained only the stearate.

EXAMPLE 7 Other surfactants may be used in a manner similar to that described for Tween 61. To a slurry of 300 g. of 40% BiOCl by weight on mica in 900 ml. of distilled water a hot dispersion of 3 g. of sodium stearate in 390 ml. of distilled water was added with stirring during 20 minutes. A solution of 0.75 g. of CaCb ZHgO in ml. of distilled water was added dropwise to the stirred mixture. The resulting slurry was then split into three 500 ml. portions (A, B and A dispersion of l g. Hyamine lO-X in 100 ml. of distilled water was added during 15 minutes to portion A. Similarly dispersions of l g. ofTriton N-57 in 100 ml. of distilled water and 3.3 g. of 30% solution of Triton X-202 in 100 ml. of distilled water were added to portions B and C respectively. A, B and C were collected and dried. All of the treated samples were wettable, with Triton N-57 showing the greatest improvement in slip and compressibility. Other wetting agents which can be used in a similar manner are BRlJ 58, Tween 20 and Tween 81.

EXAMPLE 8 If desired, the surfactant may be added prior to precipitation of the insoluble metal salt as in the following. To a series '5 of stirred slurries of 100 g. of 40% BiOCl by weight on mica in 300 ml. of distilled water were added hot suspensions of l g. of MYRJ 52 (A), BRlJ 76 (B) or Span 60 (C) and l g. of ammonium stearate. During 15 minutes a solution of 0.25 g. of CaClg 21-1 in 50 ml. of distilled water was added dropwise to each. Suspensions A, B and C were collected, washed with 100 ml. of distilled water, dried in a steam cabinet and put through a 60 mesh sieve.

All the treated samples showed substantial improvement in cling and slip compared with the original pigment.

EXAMPLE 9 If desired, the surfactant may be added as an alcoholic solution rather-than as an aqueous dispersion as in the preceding examples. To a stirred slurry of 20 g. of 40% BiOCl by weight on mica coated with 1% calcium stearate in 200 ml. of distilled water was slowly added a solution of 0.2 g. of Arlacel 20 in 10 ml. of alcohol. The mixture was collected, washed with 100 ml. of distilled water, and dried.

EXAMPLE 1O Lauric acid, or other higher fatty acids may be substituted for ammonium stearate as follows. Into a stirred slurry of 100 g. of 40% BiOCl by weight on mica in 300 ml. of distilled water was slowly poured l g. of lauric acid dispersed with several drops of NH OH in 150 m1. of hot distilled water. During one-half hour a solution of 0.37 g. CaCl .2l-l O in 100 ml. of distilled water was added. Subsequently, a hot dispersion of l g. Tween 61 in 100 ml. of distilled water was added. The resulting suspension was collected, washed with 200 ml. of distilled water, dried in a steam cabinet, and passed through a 60 mesh sieve.

EXAMPLE 1 1 The improved compressibility of pearlescent pigments treated in accordance with the present invention can be demonstrated quantitatively with the aid of an instrument known as a Textur-O-Meter (manufactured by C. W. Brabender Instruments, Inc., South Hackensack, N. 1.). Essentially the instrument measures the resistance of the test material to compression under carefully standardized conditions. A standard weight of the test material is first compressed in a suitable container, e.g. a cylindrical dish, to a standard volume. A plunger is then pressed against the test sample and the resistance offered by the sample is measured electronically. Although not numerically reproducible, test results for different materials show a relative relationship when the tests are carried out as a series utilizing the same test conditions. g

In a series of samples tested under identical conditions, the lower the resistance the greater are the slip and compressibility (these properties being interrelated). It should be emphasized again that as used herein compressibility refers to the ease with which a material can be compressed, and not to the density or hardness of the compressed material. If the sample is in the form of a dense hard cake, its resistance to further compression will of course be high, and therefore it will be of low compressibility.

The same pearlescent base (40% bismuth oxychloride on mica platelets was treated with 1% calcium stearate alone and with 1% calcium stearate plus 1% Tween 61. The compressibility of these materials was then compared using the Textur- O-Meter (20 g. samples, 5 volts and 1/5 attenuation).

Coating Sample Calcium Stcurute Tween 61 Resistance 0 0 10.4 bl N 0 2.3 C lt 1% l .0

Using 20 g. samples compressed to equal dimensions (56 mm. diameter, 16 mm. height) and instrument settings of 5 volts and one-fifth attenuation and using a 20 mm. diameter plunger, an untreated 40% BiOCl on mica gave a peak reading of 8.50. When physically blended with 1% calcium stearate the peak reading was 9.00, indicating a decrease in its compressibility. The same pigment when coated with 1% calcium stearate and 1% Tween 61 in accordance with the present invention gave a peak reading of only 0.1 (extrapolated) under the same conditions.

Likewise a 15 g. sample of untreated TiO -mica pigment gave a peak reading of 7.30. When coated with 1% calcium stearate (cf. Example 4) the peak reading was only 2.89.

Using 20 g. samples at 10 voltsand 1/5 attenuation with a 20 mm. diameter plunger the following typical results were obtained with a 40% BiOCl on mica pigment:

TABLE 1 Stearate Wetting Agent Resistance 1% Ca Stearate 1% Tween 61 4.22 1% Ca Stearate 1% Hyamine 10-X 10.4 1% Ca Stearate 1% Triton N-57 8.64 1% Ca Stearate 1% Triton X-202 1 1.2 1% Ca Laurate 1% Tween 61 6.78

It should be noted that the two nonionic surfactants Tween 61 and Triton N-57) gave better results by this test than either the cationic (Hyamine l0-X) or or anionic (Triton X202) agent.

Another series of samples compared the effect of various metal soaps (1%) with and without 1% Tween 61. The conditions were the same as in the preceding series.

In all but one instance (nickel stearate) the Tween 61 acted synergistically with the metal soap to effect a significant reduction in the compressibility of the treated pigment.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could'be made in the above methods and products without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A pigment comprising a pearlescent substance selected from bismuth oxychloride platelets, mica platelets coated with bismuth oxychloride and mica platelets coated with titanium dioxide, the surfaces of the pigment particles being substantially completely covered with an intimate adherent precipitated coating comprising a water-insoluble metal soap and a water-insoluble surfactant, said pigment being in the form of substantially dry free-flowing particles having greater compressibility and slip than pigment particles without the coating.

2. A pigment according to claim 1 wherein the wetting agent is a nonionic surfactant having an HLB value in the range of 5 to 16.

3. A pigment according to claim 1 wherein the surfactant is a polyoxyethylene derivative having an HLB value of about 4. A pigment according to claim 1 wherein the metal soap is an alkaline earth salt of a saturated fatty acid having 12-20 carbon atoms.

5. Method for treating a pearlescent pigment selected from bismuth oxychloride platelets, mica platelets coated with bismuth oxychloride and mica platelets coated with titanium dioxide, which comprises suspending the pigment in water; dispersing a water-soluble salt of a higher fatty acid in the suspension; gradually adding to the said suspension an aqueous solution containing cations which form an insoluble soap; 

2. A pigment according to claim 1 wherein the wetting agent is a nonionic surfactant having an HLB value in the range of 5 to
 16. 3. A pigment according to claim 1 wherein the surfactant is a polyoxyethylene derivative having an HLB value of about
 10. 4. A pigment according to claim 1 wherein the metal soap is an alkaline earth salt of a saturated fatty acid having 12-20 carbon atoms.
 5. Method for treating a pearlescent pigment selected from bismuth oxychloride platelets, mica platelets coated witH bismuth oxychloride and mica platelets coated with titanium dioxide, which comprises suspending the pigment in water; dispersing a water-soluble salt of a higher fatty acid in the suspension; gradually adding to the said suspension an aqueous solution containing cations which form an insoluble soap; adding to said suspension an aqueous dispersion of a water-insoluble surfactant; and recovering the pearlescent pigment in the form of substantially dry free-flowing particles.
 6. Method of claim 5 wherein the surfactant has an HLB value in the range of 5 to
 16. 7. Method of claim 5 wherein the surfactant is a polyoxyethylene derivative having an HLB value of about
 10. 8. Method of claim 5 wherein the soap is an alkaline earth salt of a saturated fatty acid having 12-20 carbon atoms. 